| ECA | electrical control activity; electrocardioanalyzer; endothelial cytotoxic activity; enterobacterial ... |
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| FA | false aneurysm; Families Anonymous; Fanconi anemia; far advanced; fatty acid; febrile antigen; femor... |
| IA | ibotenic acid; immune adherence; immunoadsorbent; immunobiologic activity; impedance angle; indolami... |
| MSA | major serologic antigen; male-specific antigen; mannitol salt agar; Medical Services Administration;... |
| PAA | partial agonist activity; phenylacetic acid; phosphonoacetic acid; physical abilities analysis; plas... |
| solar urticaria | A form of urticaria resulting from exposure to specific light spectra; e.g., sunlight; some patients have passive-transfer antibodies and others do not. (05 Mar 2000) |
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| activity | 1. The state of being active, the ability to produce some effect, the extent of some function or action. 2. <chemistry> A thermodynamic quantity that represents the effective concentration of a solute in a nonideal solution, if concentrations are replaced by activities, the equations for equilibrium constants, electrode potentials, osmotic pressure, boiling point elevation, freezing point depression and vapour pressures of volatile solutes are converted from approximations that hold only for dilute solutions to exact equations that hold for all concentrations. The activity is equal to the product of the concentration and the activity coefficient, a dimensionless number measuring deviation from nonideality. Symbol a. The potential or true thermodynamic activity of a substance, as opposed to its molar concentration. 3. <radiobiology> The number of nuclear transitions or disintegrations occurring in a given quantity of radioactive material per unit time. The SI unit of activity is s-1. The special name for the unit of activity is becquerel (Bq). The previously used special unit of activity, curie (Ci), is being replaced by the becquerel. 1 Bq = 2.7 x E-11 Ci. 1 Ci = 3.7 x E10 Bq. 4. Optical activity. (16 Dec 1997) |
| activity coefficient | <chemistry> The factor by which the value of a concentration of a solute must be multiplied to determine its true thermodynamic activity. (06 May 1997) |
| activity cycles | Bouts of physical irritability or movement alternating with periods of quiescence. It includes biochemical activity and hormonal activity which may be cellular. These cycles are shorter than 24 hours and include sleep-wakefulness cycles and the periodic activation of the digestive system. (12 Dec 1998) |
| activity, drug | A measure of the physiological response a drug produces in the body. A less active drug produces less response (and visa versa). (12 Dec 1998) |
| blocking activity | The repression or elimination of electrical activity in the brain by the arrival of a sensory stimulus. (05 Mar 2000) |
| blood bactericidal activity | Native bactericidal property of blood due to normally occurring antibacterial substances such as beta lysin, leukin, etc. (12 Dec 1998) |
| melanoma growth stimulatory activity | Cytokine of the C X C subfamily. Potent mitogen. Activates and is chemotactic for, neutrophils. (18 Nov 1997) |
| water activity | <chemistry> An expression of the relative availability of water in a substance. Pure water has an water activity of 1.000. The water activity of a solution is one-hundredth its relative humidity. (09 Oct 1997) |
| motor activity | The physical activity of an organism as a behavioural phenomenon. (12 Dec 1998) |
| complement haemolytic activity assay | Usual screening assay for complement. Dilutions of the serum to be tested are added to antibody-coated erythrocytes and the percentage of lysis is measured. The values are expressed by ch50, haemolytic complement units per milliliter, which is the dilution of serum required to lyse 50 percent of the erythrocytes in the assay. (12 Dec 1998) |
| plasma renin activity | The estimation of renin in plasma by measuring the rate of formation of angiotensin I or II. (05 Mar 2000) |
| specific activity | 1. <chemistry> The number of activity units (whatever is appropriate) per unit of mass, volume or molarity. 2. <radiobiology> Total activity of a given nuclide per gram of a compound, element or radioactive nuclide. Perhaps most often usage, in the context of radiochemicals, the number of microcuries per micromole. (16 Dec 1997) |
| structure activity analysis | Study in which systematic variation in the structure of a compound is correlated with its activity, in an attempt to determine the characteristics of the (receptor) site at which it acts. (18 Nov 1997) |
| structure-activity relationship | The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups. Other factors contributing to structure-activity relationship include chemical reactivity, electronic effects, resonance, and inductive effects. (12 Dec 1998) |